I was in a Volkswagen rental last week and the Carplay integration was a disaster. 50% of the time, attempting to play a song on spotify would crash Carplay. It would refuse to work again (or hey, crash again) until you'd left the car off for a lengthy amount of time. Presumably the car turns off the infotainment system at some point, so this is a reboot, but there was no way to reboot manually... So it would remain broken for the drive.

Seems like manufacturers aren't integrating particularly robust systems on the average

I've owned a VW for 6 years and Carplay has always worked flawlessly.

I think CarPlay (both wired and wireless versions) requires Bluetooth.

I’ve never used a wireless version of CarPlay, I always plugged it in which worked reliably in every modern budget car I’ve rented (Toyota included).